TDB can run on 32 bit or 64 bit JVMs. It adapts to the underlying architecture by choosing different file access mechanisms. 64 bit Java is preferred for large scale and production deployments. On 64 bit Java, TDB uses memory mapped files.
On 32 bit platforms, TDB uses in-heap caching of file data. In practice, the JVM heap size should be set to at least 1Gbyte. While there is no inherent scaling limits on the size of the database but, in practice, only one large dataset can be handled per TDB instance.
The on-disk file format is compatible between 32 and 64 bit systems and databases can be transferred between systems by file copy if the databases are not in use (no TDB instance is accessing them at the time). Databases can not be copied while TDB is running, even if TDB is not actively processing a query or update.